1. Field of the Invention
The present invention relates to magnetic sensors used for hard disc devices, magnetic sensing devices, and the like, and more particularly, relates to a magnetic sensor and a manufacturing method thereof, the magnetic sensor being capable of improving reproduction output due to the increase in rate of change in magnetoresistance achieved by enhancing fixing forces of fixed magnetic layers.
2. Description of the Related Art
Concomitant with increase in recording density realized in recent years, in magnetic sensors used for hard disc drives, magnetic sensing devices, and the like, a spin valve type device using a giant magnetoresistive effect has become a mainstream technique.
Since having a high reproduction sensitivity, this spin valve type magnetic sensor has drawn attention as a magnetic sensor capable of satisfying the requirements for higher recording density; however, the increase in rate ΔR/R of the change of magnetoresistance must also be realized in order to decrease a track width, which decrease has been increasingly required to satisfy the trend toward further increase in recording density in the future. In addition, the decrease in distance between a lower gap layer and an upper gap layer has also been required.
Accordingly, a so-called recessed spin valve type magnetic sensor has been proposed. The structure of this magnetic sensor is shown in FIG. 40. FIG. 40 is a cross-sectional view of the magnetic sensor when viewed from a facing surface facing a recording medium.
As shown in FIG. 40, a lower shield layer 1 is formed on a substrate which is not shown in the figure. On this lower shield layer 1, a lower gap layer 2 made of Al2O3 (aluminum oxide) or the like is formed. A pair of recess portions 2a is formed in the lower gap layer 2 with a predetermined space therebetween in a track width direction, and on an upper surface of a protruding portion 2b sandwiched between the recess portions 2a, a seed layer 3 is provided.
On this seed layer 3, a free magnetic layer 4, a first non-magnetic material layer 5, and a fixed magnetic layer 6 are provided in that order from the bottom. This fixed magnetic layer 6 has a synthetic ferrimagnetic structure formed of three layers, that is, a first fixed magnetic sublayer 6a, a second non-magnetic material sublayer 6b, and a second fixed magnetic sublayer 6c in that order from the bottom. The free magnetic layer 4, the non-magnetic material layer 5, and the fixed magnetic layer 6 collectively form a multilayer film 20.
Inside the recess portions 2a provided at two sides of the multilayer film 20, insulating layers 7 are formed, and on the insulating layers 7, hard magnetic layers 8 are formed.
As shown in FIG. 40, the fixed magnetic layer 6 is formed to extend onto the hard magnetic layers 8 formed at the two sides of the multilayer film 20.
On the fixed magnetic layer 6, a pair of antiferromagnetic layers 9 is formed with a predetermined space W1 therebetween in the track width direction. As shown in FIG. 40, the antiferromagnetic layers 9 are formed on two side regions 6d of the fixed magnetic layer 6.
On the antiferromagnetic layers 9, electrode layers 11 are formed with protective layers 10 interposed therebetween, and on the electrode layers 11, protective layers 12 are formed.
In the magnetic sensor shown in FIG. 40, a track width Tw is determined by the length of the free magnetic layer 4 in the track width direction, and the space W1 between the antiferromagnetic layers 9 is formed larger than the track width Tw.
The antiferromagnetic layer 9 generates an exchange anisotropic magnetic field at the interface with the fixed magnetic layer 6 so that the magnetization direction thereof is fixed in a Y direction in the figure.
When an exterior magnetic field such as a leakage magnetic field from a recording medium is applied to the magnetic sensor shown in FIG. 40, the magnetization direction of the free magnetic layer 4 is changed, and as a result, the electrical resistance of the multilayer film 20 is changed which is composed of the free magnetic layer 4, the first non-magnetic material layer 5, and the fixed magnetic layer 6. When this change in electrical resistance is obtained as the change in voltage or the change in current, the exterior magnetic field is detected.
In the magnetic sensor shown in FIG. 40, the structure is formed in which the space W1 between the antiferromagnetic layers 9 is formed larger than the track width Tw, and in which the antiferromagnetic layer 9 is not formed in the region of the track width Tw. Accordingly, in the region of the track width Tw, current passing between the electrode layers 11 passes through the seed layer 3, the free magnetic layer 4, the first non-magnetic material layer 5, and the fixed magnetic layer 6 and does not pass through the antiferromagnetic layer 9. Hence, compared to a magnetic sensor in which the antiferromagnetic layer 9 is formed in the region of the track width Tw, the decrease in rate ΔR/R of change in resistance (shunt loss) caused by shunt of the current described above can be reduced, and hence the output can be improved.
A magnetic sensor in which hard magnetic layers are provided at two sides of a magnetoresistive film formed of the multilayer film 20 has been disclosed in Japanese Unexamined Patent Application Publication No. 2002-305338, and a magnetic sensor in which hard magnetic layers and antiferromagnetic layers are provide at two sides of a magnetoresistive film has been disclosed in Japanese Unexamined Patent Application Publication No. 2002-289945.
However, in the magnetic sensor shown in FIG. 40, the space W1 between the antiferromagnetic layers 9 is larger than the track width Tw, and in the region of the track width Tw, the fixed magnetic layer 6 and the antiferromagnetic layer 9 are not directly exchange-coupled to each other. That is, the antiferromagnetic layers 9 are directly exchange-coupled to the fixed magnetic layer 6 at the two side regions 6d thereof. Hence, fixing forces of the fixed magnetic layer 6 at the two side regions 6d are transmitted to the region of the track width Tw, and as a result, the magnetization of the fixed magnetic layer 6 in the track width region is fixed.
Accordingly, in the magnetic sensor shown in FIG. 40, the fixing force of the fixed magnetic layer 6 in the track width region cannot be sufficiently increased.
On the other hand, in order to increase the fixing force of the fixed magnetic layer 6 in the track width region, the decrease of the space W1 may be considered; however, when the space described above is decreased, it becomes difficult to ensure the accuracy of the space W1 in manufacturing, and the case may occur in some cases in which the antiferromagnetic layers extend inside the track width region. Hence, it has been difficult to accurately obtain the space W1 between the antiferromagnetic layers 9.